Author's Note: I made Harry male, I'm afraid it just fitted better with the story. My only (other) justification is that in the books, Harry Watson is male. And dead. Okay, you're lucky I let Harry live.

It was traditional for the second son in the Royal Family to do a spell in the Armed Forces, and HRH John H. Watson wasn't an exception. His father was a stickler for tradition and he was confident that it would do John some good. John had wanted to train in medicine, but his father had considered that unnecessary. Why should he bother to train for medicine when he was expected to marry some foreign princess and rule over that kingdom? John had fought hard and in the end he was allowed to join the Navy (as opposed to the Air Force, which his father had wanted him to join) but he had had to give up on the "whole damned medicine business."

The ship that was supposed to bring him back home was becalmed, of all things. John limped over to the side of the ship, leaning on the cane he'd been given. Twenty four and left with a limp, he thought bitterly to himself. Not to mention an ugly scar that clung onto his shoulder. His father would not be glad to see him, John thought to himself. What kind of a king wanted a son who had PTSD, and a psychosomatic limp? Smiling out at the still waters, John remembered the stories that Harry used to tell him.

Deep under the waters, far deeper than you could swim – Deeper than you could swim, Harry? – Yes John, deeper than I could swim, deeper than any cable could measure and deeper than three hundred church spires could reach, live the merfolk. They are like us, but they have fish tails instead of legs like you and me.

That was how they used to start. They were quite innocent when he was younger but when he was older they followed darker themes, such as mermaids entrancing sailors with their songs, causing them to go mad and jump over side to be with them, wanting to reach the beautiful land, but it is only their cold bodies that reach there. The merfolk then eat them raw, tearing at them with teeth as sharp as daggers.

John's father never liked Harry telling him those stories, so Harry had stopped in time. He had learnt how to deal with all king like affairs, and what he needed to do when their father died. Harry had married a young woman from a nearby kingdom (a political match). John liked Clara, and she had seemed to make his older brother happy at first, but now they seemed unhappier together and the entire family had to pretend not to see how fast Harry's wine glass emptied at state occasions. John sincerely regretted the bond that had been lost between them, but no matter how hard he tried to fix it, it was never the same.

The humans had chased the merfolk deep beneath the warm surface of the seas aeons ago. Merfolk still loved the light though, drawn to it throughout all their lives. So they lived in the pleasant warmer spots in the sea, so far out that even if a human was looking for them they should not find them. After all, they knew how to hide.

Sherlock's great-great-grandfather had passed the law that meant that merfolk were strictly forbidden from visiting the surface as they used to. This was a rule that Sherlock frequently broke. He had been thirteen the first time that he had worked up the courage to break such a significant rule. He had not known he could breathe through his nose and mouth and didn't have to take in water through the gills in the side of his neck so he'd dipped constantly back under the waves, still exhilarated at all the new sights. Now he knew better.

When Sherlock was even younger he used to go exploring the sunken wrecks, revelling in delight at the beautiful objects he made care to hide away. Over the years he threw away much of the junk, but he kept a few objects. The bag of polished marbles, the strange wooden instrument that seemed fragile with the strings drawn across it that had perished away and the skull from a skeleton he found slumped over the ships wheel, bits of algae growing on the bones, though he had managed to clean most of it off the skull.

At twenty-one years of age, the surface held fewer mysteries for him than before but he still went there regularly, fascinated with the world of the humans. The only one who knew of this habit was his friend Victor, and he often covered for him. Today Sherlock saw a ship so like the wrecks he often saw. Sherlock hid himself in the water, and moved closer to the ship and looked up at the man who was staring at the sea. Sherlock saw the human's eyes move near to him, as though he'd seen him move. Sherlock shrank nearer to the ship, hiding in the shadows. He stayed there for hours, watching people moving around on the ship, remembering his childhood fantasies.

When he was six or seven Mycroft used to tell him about how the humans walked around. How they danced, how they had lands with forests in the air with creatures similar to fish that swam in this cold dry thing called air, though Sherlock understood air far better than Mycroft could now. Mycroft used to tell him of sea battles and how the humans used to catch merfolk and kill them to eat them. How they took them back for show. Sherlock used to tell him he'd become a krodan, their word for the merfolk that used to lure sailors to their deaths. Mycroft would laugh at him.

Sherlock was beginning to drift away, satisfied, when the rain fell down. He smiled, loving storms. He'd often ride the strongest currents under and above the sea, dragging along Victor very often, though he'd complain that they were getting far too old for this now. It was clear that the sailors did not love the storms the way Sherlock did as they ran around, suddenly in frenzied action. Sherlock was blinded as lightening hit the ship, the waves in the water dragging him farther away, now he was struggling to move closer. He could smell the burning wood before he saw it. Men were trying to get into lifeboats that were being tossed around like the rag doll Sherlock found on the surface when he was fifteen. He watched the humans curiously, hiding under the carved stern that had broken off the ship. He wondered where that man was, the one who held the stick and had hair like sandstone.

Sherlock slipped under the water easily, smiling as he saw the man sink. Perhaps he could come down and Sherlock could show him the world under the water. The man seemed so grim... Sherlock propelled himself towards the man, and saw his eyes closing slowly. He remembered how it felt when he forgot to breathe above the sea level and wondered whether that was how the human felt now. No. He couldn't join Sherlock's world. He wrapped his arms under the man's armpits, pulling him upwards to the surface, though the man's eyes did not open. Sherlock rode the currents through the next day, keeping the man's head above water, trying to give him his own body heat when the human's seemed to be failing.

Sherlock wondered whether he'd ever get the human to a safe place when they washed up in a cove that was still deep up until the sand. He managed to get the human onto the sand but still he didn't wake up. He stayed for a long time, hoping to see the man wake up, though he never did. He swam away slowly, taking a further two days to get back to his home, his mind still with the man whose shirt had clung to him, who had a limp, who had hair like sandstone and who had bumpy skin that Sherlock supposed was a scar. It looked like a lazy scrawl, he thought to himself, smiling.